The nervous system is responsible for accumulating and analyzing sensory input and coordinating the generation of the appropriate functional response. The successful execution and integration of these activities is dependent on the transmission of neuronal action potentials, electrical signals required to generate functional outputs. While it is the neuronal cell that is responsible for the actual conduction of the signaling current, the rate at which the signal travels is greatly enhanced by the insulating properties of its glial-derived myelin sheath. In the central nervous system (CNS), glial cells known as oligodendrocytes are responsible for the formation of myelin. These terminally differentiated cells arise from progenitors termed oligodendrocyte precursor cells (OPCs). During development, OPCs are exposed to proliferative signals as they migrate along axons throughout the CNS. These developmental cues help ensure that the extent of OPC proliferation is sufficient to generate the appropriate number of oligodendrocytes to myelinate all relevant axonal segments. Once the required number of precursor cells has been generated, the differentiation process initiates followed by myelination.
Therefore, the impacts on the myelination process by brain nutrients are integrated by three basic aspects: (1) the survival and proliferation of oligodendritic projector cells (OPCs); (2) the differentiation of OPCs into oligodendric cells (Oligo); and myelination deposition.
Myelination and synapse development are very important for neurological health. This is true in infants and children, for brain development and to provide improvement in specific brain function such as cognition, memory function, learning capacity, social interaction skills, reduced anxiety, visual acuity, motor skills and/or language skills. Likewise, improved myelination and synapse development can be beneficial in adults, especially adults with neurodegenerative diseases like Alzheimer's disease.
Myelination can be described as the process by which a fatty layer, called myelin, accumulates around nerve cells (neurons), and begins in infancy and continues through adulthood. Myelin particularly forms around the long shaft, or axon, of neurons. Myelination enables nerve cells to transmit information faster and allows for more complex brain processes. Thus, the process is vitally important to healthy central nervous system functioning.
In the nervous system, a synapse is a structure that permits a neuron to pass an electrical or chemical signal to another cell (neural or otherwise). Thus, synapses are essential to neuronal function: neurons are cells that are specialized to pass signals to individual target cells, and synapses are the means by which they do so. At a synapse, the plasma membrane of the signal-passing neuron (the presynaptic neuron) comes into close apposition with the membrane of the target (postsynaptic) cell. Both the presynaptic and postsynaptic sites contain extensive arrays of molecular machinery that link the two membranes together and carry out the signaling process. Synapse development, or synaptogenesis, is the formation of synapses between neurons in the nervous system. Although it occurs throughout a healthy person's lifespan, an explosion of synapse formation occurs during early brain development, known as exuberant synaptogenesis.
Myelination begins in the brain stem and cerebellum before birth, but is not completed in the frontal cortex until late in adolescence. Breast feeding contributes to more rapid myelination in the brain. Identification of nutrients that promote survival and proliferation of oligodendrocytes represents a major unmet need. Beyond normal development, white matter injury is one of the leading causes of neurological disease in infants, especially in infants born premature. In these cases, oligodendrocyte cell death and a lack of developmental myelination represent leading factors, resulting in aberrant neural circuit formation and nervous system refinement.
Thus, it would be useful to provide nutritional compositions that are able to improve myelination and synapse development in a subject. In particular, it may be useful to provide improved neurological health and function, including cognition, language development and motor skills in early life in order to reduce or prevent adult neurological diseases. It would also be useful to combat neurodegenerative disease through improved myelination and synapse development in adults.
Accordingly, the present disclosure provides a nutritional composition including inositol as described herein. In some embodiments, the nutritional composition also includes a fat or lipid, carbohydrate and protein or protein equivalent source.